Seleucid Kingdom. Seleucus II (246-226 BC). AR tetradrachm (16.81 gm). Uncertain Mint 40, in Commagene. 

Diademed head of Seleucus II right, with long, curly sideburn.
BASILEWS SELEYKOY, Apollo standing left, examining arrow held in right hand and resting left elbow on tall tripod, 

NP monogram in outer right field. 
Unpublished; cf. SC 727 (same obverse die, first re-engraving). 
Rare.

Virtually the entire coinage of this mint was struck from a single obverse die, which developed a flaw on the back of the king's neck. The die was reengraved which changed the portrait, but failed to correct the die flaw.
The first (as this coin) removed the bump on the bridge of the king's nose, lengthened his sideburn, and straightened his diadem ties. 

With permission of Freeman & Sear - Gemini I, Session 1 Lot: 200, Jan 2005.